Heretofore, Patent Literature 1 has been disclosed as a parking assistance system for wireless power supply. The parking assistance system disclosed in Patent Literature 1 guides a vehicle by displaying an image shot by a rear camera while the vehicle is moving backward to park. Then, when a power supply unit is hidden under the vehicle body and cannot be shot anymore, the parking assistance system supplies weak power from the power supply unit to a power reception unit, and calculates a distance between the power supply unit and the power reception unit according to a received power voltage measured at the power reception unit, thereby judging the position of the vehicle.